Preparation of two-sided mosaic



Aug. 25, 1953 ca. K. TEAL PREPARATION OF TWO-SIDED MOSAIC Filed Dec. 29,1948 FIG.

FIG. 9

INVENTOR G. TEAL W JjI/Hfi' ATTORNEY Patented Aug. 25, 1953 PREPARATIONOF TWO-SIDED MOSAIC Gordon K. Teal, Summit N. J assignor to BellTelephone Laboratories, York, N. Y., a corporation Incorporated, New

01' New York Application December 29, 1948, Serial No. 67,915

3 Claims.

This invention relates to electro-optical devices and more specificallyto methods of making target or screen structures for use in televisiontransmitter tubes.

It has long been recognized in the development of electron camera tubesfor generating picture signals at a television transmitting station thatthere are many advantages in projecting an electron image of the objectfor transmission onto one side of the screen of the tube and scanningthe opposite side of the screen with a cathode ray beam formed in thetube. An example of a camera tube employing such a two-sided? target orscreen is the so-called image orthicon" tube described in an articleentitled The image orthicon-A sensitive television pick-up tube) byAlbert Rose, Paul K. Weimer and Harold B. Law, appearing in the July1946 issue of the Proceedings of the I. R. E., beginning on page 424.The two-sided target makes possible the separation of charging anddischarging processes so that the sensitizing procedures and electricfields appropriate to each can be incorporated in the tube withoutmutual interference. The target must conduct charges between its twosides or surfaces but not along either surface. Moreover, it should havea conducting elemen therein or nearby to act as the common capacitorplate for the separate picture elements. it has been found very dimcultto construct satisfactorily commercial targets of this type.

It is an object of the present invention to pro vide novel and improvedmethods for making two-sided electron camera tube targets which have alarge number of elemental, discrete conducting elements per square inch.

In accordance with an exemplary embodiment of the invention, a magneticprocess of-making a two-sided mosaic screen or target suitable forelectron camera tubes is employed. A magnetic pole-piece is covered withwax and a number of tiny permanent magnets are sifted onto the wax sothat they are drawn to it by the pole-piece and have their ends buriedin the wax. A suitable substance such as plaster of Paris is placedaround the wires and the wax then removed. The tops of the wires arecovered with an insulator and nickel is evaporated or electroplated ontothe insulator. The top of the metal is smoothed and a conducting film,such as aluminum, for example, is evaporated onto the smooth surface.The plaster is then removed, a silver head (an enlargement of the end ofthe wire) is electroplated on each wire and the conducting film isdissolved ofl, leaving a two-sided mosaic screen.

The invention will be more readily understood by referring to thefollowing description taken in connection with the accompanying drawingforming a part thereof, in which:

Figs. 1. to 8, inclusive, illustrate various steps in a process, inaccordance with the invention, ofmaking a two-sided screen or targetstructure for use in television transmitter tubes;

Fig. 9 is top tion, in greatly target made in and Fig. 10 is a sectionalschematic side view of portions of a target of the type shown in Fig. 9.

Referring more particularly to the drawing, Figs. 9 and 10 show, by wayof example for purposes of illustration, portions of a two-sided mosaictarget suitable for use in certain television transmitting tubes suchas, for example, the image orthicon briefly referred to above. Thistarget It) comprises a thin metallic screen 25 of a suitable material,such as nickel, having a large number of holes to the linear inch, e.g., 400 to enlarged form, of a portion of a accordance with theinvention;

interior of all these apertures is filled with metallic plugs 22 havingheads 28 thereon. Successive steps in the preparation of the screen ortarget ID will be easily understood by referring to. Figs. 1 to 8,inclusive.

Considering now in detail the various steps in the process, an iron ornickel wire is permanently magnetized longitudinally and then cut intoshort for example .005 inch to .001 inch. Next, the pole-piece of astrong electromagnet 20 is coated with a thin film of wax 2|, as shownin Fig. 1. The small permanent magnets previously formed are then siftedthrough a sieve of non-magnetic material so that they will be drawn tothe wax coated polepiece 20 of the magnet. This step is accomplished invacuo, if necessary. The tiny magnets are small electromagnets 22perpendicular to the surface of the wax coating 2|.

Very fine plaster of Paris is then applied to coating 2| is then meltedand the traces remaining removed with a solvent, such as carbon view ofa schematic representatetrachloride, for example. The wires 22 are thusimbedded in the plaster base 23, as shown in Fig. 3. Magnesium or othersuitable metal is then evaporated on the unit and oxidized to form acoating 24 of magnesium oxide around the ends of the wires 22, as shownin Fig. 4. Melted glass can be used, instead of the magnesium oxide. A

nickel coating, 2-5 then evaporated: on:th'e uni-11,, as showninFi'grfi, to give-a conducting film. The film 25 is built up byevaporation or by electro plating.

The structure shown in Fig. 5, issthenibuiiede on its top surface withfine emery'or other suitable bufiing material to expose theeemls ioftthewires 22 and thus to produce the un t -sliowri in A conducting film ofaluminum; for"- Fig. 6. example, 26 is then evaporatedvuponz thesunitand this film 25 is attached to a block of wax '21.

The plaster of Paris 23 is then ground or 'dis solved off. The unit atthis stage of the processrisjshown in Fig. 71 which .isz-upsideldOWIliIWithl:

reference to Figs. 31to-16=.

Silver heads 28 arethen. electroplated; on thenickel wires 22. The wax.2.1'fis: therrdissolyed with carbon tetrachloride. and the. aluminumfilm 25' is dissolved with potassium hydroxide;

respectively. The completed: unit .is' shown: in

Fig. 8" which is similar to Fig. 10' except that-it isdrawn to a muchsmaller: scale.

Obviously, various modificationscanbe: made By way of ex-- in theprocess described above. ample,- the step where. nickel= isevaporated onthe unit. to give a conducting film: can be elimi' nated if it isdesiredto-make a grid mosaic which isof the non-barriergrid type.

What is claimed is 1. The method of preparing a two-sidedmosaic screenor target which: comprises-the steps of placing asticky ooating on amagnetic pole-piece, dropping amultiplicity-of tiny magnetic' wires-uponsaid sticky substance to b'e held in a substantially vertical 'posi-tionwithrespect tothesurface of said substance by-the= action of saidpole-piece, removing the -pole-pieee; embed--- dingthe'exposed end-ofeach wire in'aisupport member, removing the sticky coating; coveringeach ofthe then exposed ends of said wires with: insulating material,filling in the-spaces between said insulated wires with conductingmaterial} bufling said conducting material to exposethe covered end ofeach of said wiresand; to-fern'r a smooth surface of conducting materialinter spaced with insulating material; removing-the support membertoexpose-the other' end of each of said wires, and electroplating head'sof--metal-- lie material on the ends of-said wires exposed bythe removalof the support-member.--

2 The method of preparing a two-sided" mosaic screen or target whichcomprises the steps of forming an array of individual tiny wires ofmagnetic material arranged substantially parallel to one another bymagnetic means, covering each of said wires with insulating material,filling in the spaces between said insulated wires with conductingmaterial, buffing sai'dlconducting material .toi-exposerthe covered end'of each of said wires-"and to form a smooth surface of conductingmaterial interspersed with insulating material, removing the supportmembertaexposathemther end of each of said wires, and electroplatingheads of metallic material on -tlieends of said wires exposed by theremoval oftliesupportmember.

'3: The 'meth"od of preparing a two-sided .j mosaic; screen. or, targetwhich comprises the steps of placing a sticky coating on a magneticpolepi'ece rdropping a multiplicity of tiny magnetic wires upon saidsticky coating to be held in a substantially'verticakpositiomwitlr'respectito the surface of said substance by theactionzoiasaidi pole-piece; removing; the poleepiece', embedding theupper side of said wires in assupportingl subs stance removingthe stickycoating, reversingithe supporting substance and the member. carried;thereby; applying insulationflaroundrthez-exp'osedz upper ends ofsai'dwiresforming'aiconducting; coatingbetween and over. the: insulated:wires-s buffing said conducting coating to-.:.exposel. than covered endsof said wires andto; iornr'a smoothi; surf ace-of conducting material.interspersedtwithl; insulating material, applying: aam-etallic :coating:

to the smooth surface, applying a second. sup:

--porting substance to said" metallic coating," re movingthefirst-mentioned: supporting: sub-- stance, reversing the secondsupporting: sub'estance and the member "carried therebiy to; expose;vthe wires at-the-upper part thereof, electroplate 7 ingheadsof metallicmateriat on the -exposedf ends-of said wires, andthen removing-thesecond supporting substance.-

GORDQN K References Cited; in the file 110i this; patent? UNITED STATES;PA'IENTS;

1. THE METHOD OF PREPARING A TWO-SIDED MOSAIC SCREEN OR TARGET WHICH COMPRISES THE STEPS OF PLACING A STICKY COATING ON A MAGNETIC POLE-PIECE, DROPPING A MULTIPLICITY OF TINY MAGNETIC WIRES UPON SAID STICKY SUBSTANCE TO BE HELD IN A SUBSTANTIALLY VERTICAL POSITION WITH RESPECT TO THE SURFACE OF SAID SUBSTANCE BY THE ACTION OF SAID POLE-PIECE, REMOVING THE POLE-PIECE, EMBEDDING THE EXPOSED END OF EACH WIRE IN A SUPPORT MEMBER, REMOVING THE STICKY COATING COVERING EACH OF THE THEN EXPOSED ENDS OF SAID WIRES WITH INSULATING MATERIAL, FILLING IN THE SPACES BETWEEN SAID INSULATED WIRES WITH CONDUCTING MATERIAL, BUFFING SAID CONDUCTING MATERIAL TO EXPOSE THE COVERED END OF EACH OF SAID WIRES AND TO FORM A SMOOTH SURFACE OF CONDUCTING MATERIAL INTERSPACED WITH INSULATING MATERIAL, REMOVING THE SUPPORT MEMBER TO EXPOSE THE OTHER END OF EACH OF SAID WIRES, AND ELECTROPLATING HEADS OF METALLIC MATERIAL ON THE ENDS OF SAID WIRES EXPOSED BY THE REMOVAL OF THE SUPPORT MEMBER. 